Soap



A. FINSBERG July 31, 1962 SOAP 3 Sheets-Sheet 1 Filed Oct. 14, 1957 INVENTOR ARNE FINSBERG HIS ATTORNEYS A. FINSBERG July 31, 1962 SOAP Filed Oct. 14, 1957 5 Sheets-Sheet 2 INVENTOR ARNE FINSBERG HIS ATTORNEYS July 31, 1962 Filed Oct. 14, 1957 A. FINSBERG 3,047,600

SOAP

5 Sheets-Sheet I5 INVENTOR ARNE FINSBERG BY W fa.

HIS ATTORNEYS 3,047,600 Patented July 31, 1962 3,047,600 SOAP Arne Finsberg, Oslo, Norway, assignor to Lever Brothers Company, New York, N.Y., a corporation of Maine Filed Oct. 14, 1957, Ser. No. 690,127 Claims priority, application Great Britain Oct. 19, 1956 18 Claims. (Cl. 260419) The present invention relates to the manufacture of soap and in particular to the extraction of glycerine from soap produced by the saponification of fats and fatty oils, hereinafter for convenience referred to as fats.

In the orthodox manufacture of soap, as, for example, explained in the introduction to British Patent 612,014, the fats are generally boiled, by means of open steam, with caustic soda solution in large open pans.

It is customary next to separate the soap as far as possible from the resulting homogeneous mixture of soap and aqueous liquor containing the glycerine, by adding a quantity of electrolyte (hereinafter referred to as salt), such as sodium chloride or concentrated brine, whereupon the homogeneous mass settles in two layers, the upper consisting of the soap and the lower layer, caller lye, being an aqueous solution of the salt, glycerine and impurities from the fats. The soap so separated, a curd, usually contains of the order of 63% of fatty matter. By lye is meant a solution of salt, the concentration of which is at least so great that soap will not dissolve in it (the critical concentration). After satisfactory separation, the lye is run ofl, purified and evaporated for the recovery of glycerine and salt. The curd soap which remains in the pan is boiled with a suitable amount of water to close the curd. The contents of the pan are then again opened by addition of salt. If this process is repeated a number of times, most of the glycerine can be Washed, that is, extracted from the soap.

The soap is next fitted to separate it into an upper layer of neat soap and a lower layer of nigre. This fitting operation is described in the introduction to British Patent 623,224.

The orthodox soap-making process outlined above may advantageously be substituted by continuous processes, or a series or" processes where one or two of the three steps referred to are continuous. Especially the continuous washing of soap offers considerable advantages; continuous extraction of glycerine from soap may be more complete or cost less than batchwise extraction. It has previously been proposed to Wash soap continuously by mixing intimately a continuous stream of soap with a continuous stream of brine at or above the critical concentration, thus facilitating the removal of glycerine from the soap to the lye, and then allowing the lye to separate from the soap. This separation may take place according to the method described in British Patent 612,014. The degree of washing of the soap is generally determined by economic considerations; a great quantity of lye allows almost complete extraction of glycerine (but it becomes expensive to evaporate the lye); a smaller quantity, economical to evaporate, will allow less complete extraction.

It is an object of the present invention to provide an improved process for continuously washing soap. The process for washing soap according to the invention is one in which unwashed soap and fresh lye are continuously supplied to a vessel, the soap to be Washed is intimately mixed with fresh lye, the lye is separated from the soap, and separated soap and lye are continuously removed from the vessel, a portion of the lye continuously removed being returned and directly mixed with the soap which is washed with the fresh lye, this portion of separated lye being at least equal in weight to the quantity of fresh lye introduced.

Fresh lye may be lye free from glycerine or lye already containing some glycerine; for instance it may already have been used to wash soap of lower glycerine content.

Preferably the fresh lye to be intimately mixed with the soap is in the form of a continuous stream, and preferably also the soap to be intimately mixed with the fresh lye is in the form of a continuous stream. The soap to be washed and the portion of returned separated lye are advantageously mixed separately of the bulk of soap and lye contained in the vessel in which separation takes place. The mixing can be altogether outside the vessel or it can be in a compartment within the vessel. The fresh lye can also be mixed with the soap to be washed, separately from the bulk of soap and lye contained in the vessel in which separation takes place. Conveniently the washing by separate mixing is substantially complete before the mixture enters that part of the vessel where separation takes place. Separate mixing can take place in a tube through which the mixture flows to that part of the vessel where separation takes place.

Particularly satisfactory results can be obtained when the portion of separated lye removed from the vessel, returned and directly mixed with the soap is at least three times the weight of the fresh lye introduced. The portion may be as much as five or ten times the weight of fresh lye introduced if this is desired.

The process is conveniently carried out in a series of vessels, in each of which a washing operation takes place. Thus the soap and lye can be passed through at least two vessels in series, in each of which the process of the invention is carried out, and the soap and the lye passing through the series of vessels can be counter-current, that is to say, the general movement of lye transported through the series of vessels is in the opposite direction to that of the soap. The series of vessels can take the form of a number of compartments into which a large soap pan is divided by partitions.

Suitable apparatus for carrying out the process of the invention comprises at least two vessels in series, each of which is provided with a mixing device discharging into it, the mixing device of any vessel subsequent to the first vessel of the series being arranged within the preceding vessel. Preferably the mixing device of every vessel subsequent to the first one is arranged within the preceding vessel. The mixing device of the first vessel is preferably arranged within the last vessel.

in a particularly suitable form of apparatus, the inlet of a mixing device is centrally disposed in the preceding vessel and is, except for the mixing device of the first vessel, arranged so that liquid contained in the vessel within which the mixing device is disposed can overflow into that mixing device. Means can be provided for introducing liquid from any vessel into the mixing device arranged in any preceding vessel. Means can also be provided for promoting the flow of liquid through the mixing device, and an ejector can be used; with an ejector, a stream of one liquid is forced through a constricted orifice within a tube carrying another liquid, which is thus drawn along the tube.

The invention will now be described with reference to the accompanying drawings, in which FIGURES 1 to 7 each show a diagrammatic flow sheet of a particular way of carrying out the invention, and FIGURE 8 shows diagrammatically a mixing device.

FIGURE 1 shows diagrammatically in section a soap pan in which a layer of molten soap S floats on a layer of lye L. It is known to introduce the soap through a conduit 3 and let it pass through the layer of lye, while the lye is introduced through a conduit 1, where it mixes with the soap and then separates by gravity in counter-current with soap rising from the layer of lye. The soap is removed from the system at 2, for instance by overflowing, and at 4 the lye, which is now enriched with glycerine, is

allowed to leave the pan at the same rate at which it is introduced. According to the present invention some of the already separate lye from layer L is recycled through a conduit 5 via pump 6 to the top of the soap layer S and introduced into the soap layer by a convenient diffuser 7 in such a way as to mix with the soap into which the lye from the conduit 1, centers the quantity of separated lye recycled being at least equal in weight to the lye entering from the conduit 1. This arrangement affects increased washing of the soap. The theoretical equilibrium is approached, that is, the glycerine concentration in the soap and in the lye which have come into intimate contact will not change even after prolonged extraction.

It will be appreciated from the drawing that the present invention allows a wide choice of arrangements for introducing or removing soap and lye into or from the pan. Under certain circumstances the soap may, for example, be introduced at 1 and the lye at 3, without affecting noticeably the result, if a sufiicient quantity of lye is circulated from the lye layer through the diffuser '1': this circulated lye includes fresh lye and recycled lye. It is evident that the quantity of circulating lye can be varied within reasonable limits without affecting the cost of the plant noticeably owing to the simplicity of the system. The wide choice of arrangements for introducing and removing the soap and lye allows the coupling of two or more units thus facilitating extremely simple constructions of combinations of such units.

The arrangement of FIGURE 2 is substantially similar to that shown in FIGURE 1 except that a vertical separating wall has been introduced into the pan. This separating wall rises above the level of the soap and dips some way into the layer of soap so as to allow the soap to pass as indicated by the arrow 3. (It is possible to extend the lower end of the separating wall beyond the soap layer without exceeding the scope of the invention, so long as the soap can pass through.) In the embodiment shown in FIGURE 2 the soap will be washed in the area Sa, then pass on to area Sb, where, by choosing convenient horizontal and vertical dimensions, any desired degree of separation can be achieved. This separation is not disturbed by the intense mixing operation in area Sa. The soap is introduced at 9 and the fresh lye at 12 into the tube 11, which also serves to recycle lye with the aid of a steam ejector 10.

A further embodiment of the invention is illustrated in FIGURE 3. It is possible to reduce the mixing area So to such dimensions that, for instance, it assumes the shape of a tube 13. The soap is introduced at 14 into a convenient widening 15 of the tube 13, meets the lye circulating by means of pumping device 18 through the tube 16, and is mixed intimately with the lye by a mixing device 17. The mixing device 17 may conveniently be a form of ejector in which the suction of the flow of lye breaks up the soap into small particles, resulting in a fine emulsion which discharges into the layer of lye from which the soap rises on separating from the lye.

One such mixing device is shown diagrammatically in FIGURE 8. A lye circulating pipe 50, cut away at its end to leave three strips to act as guides 51 for an inside cone 52, passes down a short distance within pipe 53 attached to funnel 54 into which soap curd is introduced. The force and direction of the lye, passing off the cone and through the apertures between the guides 51, provide intimate and eflicient agitation of the lye with the soap and exert suction to pull the soap from the funnel downwards and force the mixture into the settling compartment. The pressure and velocity of the lye can be controlled to some extent by raising or lowering the cone 52 within the guides 51; a screwed rod 55 and nut 56 are attached to the cone 52 for this purpose.

FIGURE 4 shows an embodiment of the invention in which two washing units are combined. The curd soap is introduced into pan II at 14- as before, and is mixed with lye circulated via conduit 16 as before. The soap then separates from the lye rising slowly and flowing over at 19 into funnel 20 situated in the adjacent pan 1, where it is again intimately mixed with circulating lye emerging from conduit 16, and together with the lye discharged into the lye layer. It rises from this layer and is finally removed from the system, overflowing at 21, having thus been twice washed with lye. Fresh lye is introduced into the system at 2 2, where it is mixed with lye already used for washing and is circulated through the conduit 16' and takes up glycerine from the soap: separated lye passes into the pan II through the aperture 23. In pan II the incoming lye is mixed with lye already circulated there and containing a higher proportion of glycerine, and the mixture is circulated and introduced with the curd soap at 14, taking up more glycerine from the curd soap; used lye is removed at 24-. In operating the process the quan tity of fresh lye introduced at 22 is adjusted to equal the quantity of lye which flows from pan I to pan II through the aperture 23, and also equals the quantity which is removed from the system at 24. Control of this quantity may be effected by interface floats 2S and 26, which actuate devices at the aperture 23 and the outflow 24 to keep the interfaces at constant levels.

Instead of providing the apertures 23 for allowing lye from pan I to flow to pan II, lye from pan I may be made to enter pan II simultaneously with the recycled lye and the curd soap. In this way the dilution of the lye in pan II by the lye from pan I containing less glycerine is reduced and also the soap receives a more effective washing treatment on entering pan II.

FIGURE 5 shows an arrangement in which four washing units are combined. To facilitate the understanding of this arrangement it is pointed out that funnel 28 (and similar funnels) receiving soap and recycled lye as well as fresh lye has been moved to the middle of the adjacent compartment. Funnel 2ft accordingly belongs to section B although it is disposed within section A. In this way soap overflows in the middle of the compartment, instead of at the edge thus reducing the average distance soap has to flow from compartment to compartment.

Fresh lye containing substantially no glycerine enters the arrangement through conduit 27 into funnel 4-1 disposed within section D. Crude curd soap enters the funnel 28 of section B through conduit 29, together with lye circulating from section B through conduit 39. Of all the lye in the various sections, lye separating in section B is richest in glycerine, and some is therefore also removed at 30 in a quantity equal to the quantity of transported lye introduced into the funnel 28 of section B at 31. This transported lye which replaces lye removed at 30 is fresh lye so far as section B is concerned, but already contains glycerine (though less than in the removed lye) and leaves the bottom of section C via a conduit and pump 39 through the valve 32, which is governed by the interface float 33, and thence through conduit 34 into the funnel 28 of section B. The quantity of lye removed from section B and not recycled is controlled by the valve 35, governed by the interface float 36. The curd soap entering funnel 28 of section B is mixed by the device 37 with the fresh lye and lye recycled from the bottom of section B by a pump 39 to the mixing device 37, and the resulting emulsion is discharged through the tube 38 into section B. In section B the soap separates from the lye by rising, and when it has reached the surface it overflows into funnel 40 of section C (disposed within section B) where it is mixed with recycled lye from section C delivered by the pump 39' as well as with fresh lye transported from section D. This operation is repeated in the remaining two sections. Section A is shown twice for an easier understanding of the process.

FIGURE 6 helps to demonstrate how the soap receives its last wash in the funnel 41 of section A (disposed within section D) by means of fresh lye 27 introduced there together with recycled lye from section A. The soap/ lye emulsion leaving funnel 41 discharges into section A and separates into an upper layer of soap and a lower layer of lye as described above. The soap overflows into gutter 42 from which the soap is removed, having received its final wash.

The position of the soap/lye interface is of no consequence for the operation of the process, and the soap/ lye emulsion may be discharged into either the lye layer or the soap layer, or into the interface itself; the choice will largely depend on economic considerations. It may be advantageous to have a deep soap layer (whereupon soap takes longer to rise and a more complete separation of lye and soap is effected) or it may be advantageous to have a relatively shallow soap layer (to reduce the qantity of soap to be washed).

FIGURE 7 shows an arrangement of six washing units.

Four or six washing units, or even greater numbers, may be cheaply and yet very compactly arranged. Thus, for example, existing soap pans may be divided into these units by simply erecting dividing walls (which may be of light and cheap material, as the walls do not have to resist high pressures).

A further advantage of the invention is that the successful operation of the process is not dependent on the condition of the soap to be washed; it may be closed or .1

open, provided it is reasonably liquid. If the soap contains large amounts of water, which would, of course, reduce the concentration of the lye below its critical concentration, then it can be rectified simply by feeding into the soap a continuous stream of concentrated brine.

A nigre can be used for washing soap according to the process of the invention. However, the addition of nigre to the first of a multi-stage washing operation as, for example, section A illustrated in FIGURE 5 is not recommended as the comparatively low content of glycerine in nigre would adversely aifect the efiiciency of the sys tem. Nigre may advantageously be added in later stages, for example, section C where the glycerine has already been removed to about the level generally found in nigre. The excess of water in nigre over the content in an ordinary curd soap can easily be rectified as described above by adding a continuous stream of concentrated brine.

The following example illustrates a process of the invention using relatively simple equipment, and the data provided can readily be adapted for a process using more elaborate equipment such as is illustrated in FIGURES 5, 6 and 7.

Example A soap pan of 3.9 x 3.9 metres cross section and 4 metres high was divided into four compartments of equal size by two dividing walls crossing each other in the centre. Each compartment was provided with a vertical wall which, when the compartment contained soap and lye, rose above the level of the soap and dipped into the soap layer to within 0.5 metre of the soap/lye interface, thus dividing each compartment into a mixing zone and a separating zone. The level of the dividing walls was such that soap could overflow by gravity from the separating zone of the first compartment to the mixing zone of the second, then to the third and fourth in turn, and finally into a gutter taking away the washed soap. Apertures in the walls of the compartments were provided enabling lye to enter the fourth compartment and pass in turn through the third, second and first compartments and out of the system.

A continuous stream of crude curd soap at 95 C. in the closed condition containing about 58% fatty acids was fed into the first compartment of the apparatus at the rate of 5 tons per hour. Counter-current to this, 3 tons of brine, containing 11.5% by weight of sodium chloride and at a temperature of 90 C., was continuously introduced into the fourth compartment. In each compartmcnt brine w-as recirculated through the soap in the mixing zone by means of a centrifugal pump at a rate of 18 tons per hour. The portion of separated lye removed from the compartments in each instance, returned and directly mixed with the soap (that is, recycled lye) was accordingly five times the weight of the fresh lye introduced. The glycerine content of the crude curd was 4% by weight and was reduced to 0.6% after the soap had been finally washed; on leaving the system the soap still had a fatty acid content of about 58%. The content of glycerine in the brine entering the first compartment was 0.2%, while 6.8% of glycerine was found in the final lye; in the intermediate compartments the content of glycerine was between these figures. An aqueous solution of caustic soda was continuously added to the brine in a quantity suflicient to keep the lye well on the alkaline side. In the gutter aqueous solutions of salt were added in suitable amounts to fit the soap, which was then allowed to settle in a pan.

I claim:

1. A process for washing soap inwhich unwashed soap is mixed with fresh lye, the mixture of soap and lye is continuously supplied to a vessel, the lye is separated from the soap and separated soap and lye are continuously removed from the vessel, a portion of the separated lye continuously removed from the vessel being intimately mixed with the mixture of unwashed soap and fresh lye continuously supplied to the vessel, said portion of separated lye being at least equal in weight to the quantity of fresh lye mixed with the unwashed soap.

2. A process according to claim 1 in which the portion of separated lye removed from the vessel, returned and intimately mixed with the mixture of unwashed soap and fresh lye continuously supplied to the vessel is at least three times the weight of the fresh lye.

3. A process according to claim 1 in which the fresh lye, the separated lye continuously removed from the vessel, and the unwashed soap which are to be mixed are each in the form. of a continuous stream.

4. A process according to claim 3 in which the unwashed soap, the portion of returned separated lye and the fresh lye are mixed separately from the bulk of soap and lye contained in the vessel in which separation takes place.

5. A process according to claim 4 in which the separate washing is substantially complete before the mixture enters that part of the vessel where separation takes place.

6. A process according to claim 4 in which the portion of separated lye removed from the Vessel, returned and intimately mixed with the mixture of unwashed soap and fresh lye continuously supplied to the vessel is at least three times the weight of the fresh lye.

7. A process according to claim 4 in which the separate mixing takes place in a tube through which the mixture fiows to that part of the vessel where separation takes place.

8. A process according to claim 4 in which the separate mixing takes place in a tube through which the mixture flows to that part of the vessel Where separation takes place.

9. A process according to claim 6 in which the separate mixing takes place in a tube through which the mixture flows to that part of the vessel where separation takes place.

10. A process for washing soap in at least two vessels in series in which unwashed soap is mixed with fresh lye, the mixture of soap and lye is continuously supplied to at least one of said vessels, the lye is separated from the soap and separated soap and lye are continuously removed from each vessel, a portion of the separated lye continuously removed from a vessel being intimately mixed with the mixture of unwashed soap and fresh lye continuously supplied to said vessel, said portion of separated lye being at least equal in weight to the quantity of fresh lye mixed with the unwashed soap.

ll. A process according to claim 10 in which the fresh lye, the separated lye continuously removed from a vessel, and the unwashed soap which are to be mixed are each in the form of a continuous stream.

12. A process according to claim 11 in which the unwashed soap, the portion of the returned separated lye and the fresh lye are mixed separately from the bulk of soap and lye contained in the vessel in which separation takes places.

13. A process according to claim 10 in which the soap and lye are passed counter-currently through the vessels in series, in each of which the process is carried out.

14. A process according to claim 11 in which the soap and lye are passed counter-currently through the vessels in series, in each of which the process is carried out.

15. A process according to claim 12 in which the soap and lye are passed counter-currently through the vessels in series, in each of which the process is carried out.

16. A process for washing soap, in which unwashed soap is mixed with fresh nigre, the mixture of soap and nigre is continuously supplied to a vessel, the nigre is separated from the soap and separated soap and nigre are continuously removed from the vessel, a portion of the separated nigre continuously removed from the vessel being intimately mixed with the mixture of unwashed soap and fresh nigre continuously supplied to the vessel, said portion of separated nigre being at least equal in weight to the quantity of fresh nigre mixed with the unwashed soap.

17. A process according to claim 16 in which the fresh nigre, the separated nigre continuously removed from the vessel and the unwashed soap which are to be mixed are each in the form of a continuous stream.

18. A process according to claim 17 in which the unwashed soap, the portion of returned separated nigre and the fresh nigre are mixed separately from the bulk of soap and nigre contained in the vessel in which separation takes place.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,047,600 July 31, 1962 Arne Finsberg It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 24, for "caller" read called column 3, line 7, for "conduit 1, centers" read conduit 1 enter-s column 6, line 53, for the claim reference numeral "4" read 5 Signed and sealed this 27th day of November 1962.

(SEAL) Attest:

ESTON Attesting Officer Commissioner of Patents 

1. A PROCESS FOR WASHING SOAP IN WHICH UNWASHED SOAP IS MIXED WITH FRESH LYE, THE MIXTURE OF SOAP AND LYE IS CONTINUOUSLY SUPPLIED TO A VESSEL, THE LYE IS SEPARATED FROM THE SOAP AND SEPARATED SOAP AND LYE ARE CONTINUOUSLY REMOVED FROM THE VESSEL, A PORTION OF THE SEPARATED LYE CONTINUOUSLY REMOVED FROM THE VESSEL BEING INTIMATELY MIXED WITH THE MIXTURE OF UNWASHED SOAP AND FRESH LYE CONTINUOUSLY SUPPLIED TO THE VESSEL, SAID PORTION OF SEPARATED LYE BEING AT LEAST EQUAL IN WEIGHT TO THE QUANTITY OF FRESH LYE MIXED WITH THE UNWASHED SOAP. 